The present invention relates to a height-adjustable folding chair.
There has been, hitherto, known a height-adjustable folding chair which has a main frame and a height-adjustable seat (U.S. Pat. No. 4,793,654). The main frame is made of a large U-shaped metal pipe and a small U-shaped metal pipe arranged in the large metal pipe with remaining vertically extending gaps. The seat has vertical plates ends of which are inserted through the vertically extending gaps and stoppers made of hard-rubber mounted on a shaft connecting left and right vertical plates at rear ends thereof mutually or projecting to the left and right sides so that the stoppers abut against the front surfaces and rear surfaces of the metal pipes of the main frame.
The chair is comfortable to sit on since the stoppers function as cushions, and the seat is continuously adjustable at any height. However, the seat is held with friction force caused by abutting the stoppers against the surfaces of pipes. Therefore, though the seat can be securely fixed to the main frame when a user sits on it, the seat might slip down when no user sits on it and an upward force is applied at the front end of the seat, since the leverage function and the friction are cancelled.
In order to delete the problem, another chair having many engaging projections capable of engaging with the stoppers at the rear surfaces of the pipe of the main frame is proposed (cf. JIKKO Hei 1-11090, Japanese Utility Model Examined Publication No. 11090/1989).
In this chair, such risk that the seat slips down is relatively small when the front end of the seat is pulled up in some extent. However, when the seat inclines to an extent, the stopper disengages from the engaging projections and the seat slips down to engage with the next projection. Further, in the worst case, the seat might fall down from the main frame.
In addition, in the above known chairs, the height-adjustable area of the seat is limited to an area upper than the connecting portion of an auxiliary leg since the auxiliary leg is rotatably connected with the main frame at a middle portion thereof. Therefore, the seat cannot be set at a lower height. Further, when the chair is folded, the seat is mounted on the main frame with the under surface out. Therefore, the mounted seat is not stable and appearance of the chair is not undesirable when it is folded.
An object of the present invention is a height-adjustable chair in which user feels comfortable to sit on, seat is hard to slip out of the main frame, and adjustable height area is wide.
Another object of the present invention is a height-adjustable chair which has good appearance when it is folded.
Further another object of the present invention is a chair pertinent to hand work, in which angle of the seat is adjustable in accordance with height of the seat or in accordance with posture of the user.